# Formula for average force?

1. Dec 9, 2007

### wyclefchick

[SOLVED] Formula for average force?

In a ballistics test at the police department, Officer Rios fires a 6.0 g bullet at 350 m/s into a container that stops it in 1.8 ms. What is the average force that stops the bullet?

can anyone help me to do this? or just give me the formula? The teacher gave us the right answer and it's -1.2 x 10^3N

Last edited by a moderator: Dec 18, 2007
2. Dec 9, 2007

### nicksauce

The average force is the change in momentum divided by the change in time.

3. Dec 9, 2007

### calcisforlovers

This is just an impulse-momentum theorem problem. Impulse = Change in momentum. Impulse is F*delta t (t=time of impact) and change in momentum is just final momentum - initial momentum. Good luck

4. Dec 9, 2007

### wyclefchick

delta p= J
and J= F(delta t)

so

delta p=6.0g(350m/s)
delta p=2100
2100/1.8=1166.6666667

is that the same thing as 1.2x10^3?

5. Dec 9, 2007

### cristo

Staff Emeritus
It would be rounded to 1.2x10^3, yes.

6. Dec 9, 2007

### wyclefchick

thank you so much guys!

7. Dec 9, 2007

### cristo

Staff Emeritus
You're welcome (I'll speak on behalf of the people that actually helped you! )